This proposal will examine the role of the spinal trigeminal nucleus in the control of the adrenal secretion of catecholamines and the cardiovascular responses evoked by peripheral and central activation of trigeminal neurons. Emphasis is directed at the intranuclear and neurochemical organization as well as the principal projection pathways of the spinal trigeminal nucleus that contribute to the adrenomedullary and autonomic aspects of nociception. Local activation of spinal trigeminal neurons by direct microinjection of glutamate or putative neurotransmitters will assess the relative contribution of rostral and caudal nuclear areas in control of adrenal and autonomic function. Peripheral trigeminal neurons are activated by mechanical radiant heat stimuli. Selective surgical interruption of central pathways or local neuronal inhibition by lidocaine microinjection will delineate the principal projection that underlie adrenal and cardiovascular responses evoked by trigeminal stimulation. Selective sampling of adrenal venous blood by lumboadrenal vein catheterization will permit estimates of adrenal secretion of catecholamines and adrenal blood flow to be determined with high resolution. Plasma catecholamines are assayed by HPLC with electrochemical detection. Carotid arterial blood flow, aortic arterial pressure, heart rate, and expiratory C02 are monitored continuously. Neurophysiological recording techniques will assess the efferent projections of spinal trigeminal neurons that may code for the adrenal and autonomic responses to noxious stimuli. Although the central neural organization that underlies the sensory- discriminative aspects of nociception has received much attention, the central neural organization that underlies the adrenal and autonomic responses to nociception is not well defined. This proposal focuses on the spinal trigeminal system as a model to assess the degree of overlap between the sensory- discriminative and the autonomic aspects of nociception.